Remove Support/IncludeFile.h and its only user. This is actively harmful, since

it breaks the modules builds (where CallGraph.h can be quite reasonably
transitively included by an unimported portion of a module, and CallGraph.cpp
not linked in), and appears to have been entirely redundant since PR780 was
fixed back in 2008.

If this breaks anything, please revert; I have only tested this with a single
configuration, and it's possible that this is still somehow fixing something
(though I doubt it, since no other similar file uses this mechanism any more).

llvm-svn: 215142

include/llvm/Analysis/CallGraph.h

@@ -58,7 +58,6 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
-#include "llvm/Support/IncludeFile.h"
 #include <map>
 
 namespace llvm {
@@ -461,7 +460,4 @@ struct GraphTraits<const CallGraph *> : public GraphTraits<
 
 } // End llvm namespace
 
-// Make sure that any clients of this file link in CallGraph.cpp
-FORCE_DEFINING_FILE_TO_BE_LINKED(CallGraph)
-
 #endif

include/llvm/Support/IncludeFile.h

@@ -1,79 +0,0 @@
-//===- llvm/Support/IncludeFile.h - Ensure Linking Of Library ---*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the FORCE_DEFINING_FILE_TO_BE_LINKED and DEFINE_FILE_FOR
-// macros.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_SUPPORT_INCLUDEFILE_H
-#define LLVM_SUPPORT_INCLUDEFILE_H
-
-/// This macro is the public interface that IncludeFile.h exports. This gives
-/// us the option to implement the "link the definition" capability in any
-/// manner that we choose. All header files that depend on a specific .cpp
-/// file being linked at run time should use this macro instead of the
-/// IncludeFile class directly.
-///
-/// For example, foo.h would use:<br/>
-/// <tt>FORCE_DEFINING_FILE_TO_BE_LINKED(foo)</tt><br/>
-///
-/// And, foo.cp would use:<br/>
-/// <tt>DEFINING_FILE_FOR(foo)</tt><br/>
-#ifdef __GNUC__
-// If the `used' attribute is available, use it to create a variable
-// with an initializer that will force the linking of the defining file.
-#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
-  namespace llvm { \
-    extern const char name ## LinkVar; \
-    __attribute__((used)) static const char *const name ## LinkObj = \
-      &name ## LinkVar; \
-  }
-#else
-// Otherwise use a constructor call.
-#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
-  namespace llvm { \
-    extern const char name ## LinkVar; \
-    static const IncludeFile name ## LinkObj ( &name ## LinkVar ); \
-  }
-#endif
-
-/// This macro is the counterpart to FORCE_DEFINING_FILE_TO_BE_LINKED. It should
-/// be used in a .cpp file to define the name referenced in a header file that
-/// will cause linkage of the .cpp file. It should only be used at extern level.
-#define DEFINING_FILE_FOR(name) \
-  namespace llvm { const char name ## LinkVar = 0; }
-
-namespace llvm {
-
-/// This class is used in the implementation of FORCE_DEFINING_FILE_TO_BE_LINKED
-/// macro to make sure that the implementation of a header file is included
-/// into a tool that uses the header.  This is solely
-/// to overcome problems linking .a files and not getting the implementation
-/// of compilation units we need. This is commonly an issue with the various
-/// Passes but also occurs elsewhere in LLVM. We like to use .a files because
-/// they link faster and provide the smallest executables. However, sometimes
-/// those executables are too small, if the program doesn't reference something
-/// that might be needed, especially by a loaded share object. This little class
-/// helps to resolve that problem. The basic strategy is to use this class in
-/// a header file and pass the address of a variable to the constructor. If the
-/// variable is defined in the header file's corresponding .cpp file then all
-/// tools/libraries that \#include the header file will require the .cpp as
-/// well.
-/// For example:<br/>
-/// <tt>extern int LinkMyCodeStub;</tt><br/>
-/// <tt>static IncludeFile LinkMyModule(&LinkMyCodeStub);</tt><br/>
-/// @brief Class to ensure linking of corresponding object file.
-struct IncludeFile {
-  explicit IncludeFile(const void *);
-};
-
-}
-
-#endif

lib/Analysis/IPA/CallGraph.cpp

@@ -282,6 +282,3 @@ void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
 #endif
-
-// Enuse that users of CallGraph.h also link with this file
-DEFINING_FILE_FOR(CallGraph)

lib/Support/CMakeLists.txt

@@ -76,7 +76,6 @@ add_llvm_library(LLVMSupport
   DynamicLibrary.cpp
   Errno.cpp
   Host.cpp
-  IncludeFile.cpp
   Memory.cpp
   Mutex.cpp
   Path.cpp

lib/Support/IncludeFile.cpp

@@ -1,20 +0,0 @@
-//===- lib/Support/IncludeFile.cpp - Ensure Linking Of Implementation -----===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the IncludeFile constructor.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/IncludeFile.h"
-
-using namespace llvm;
-
-// This constructor is used to ensure linking of other modules. See the
-// llvm/Support/IncludeFile.h header for details.
-IncludeFile::IncludeFile(const void*) {}